The present invention relates to a solid catalyst component and catalyst for polymerization of olefins, which have a high responsiveness to hydrogen and can afford olefin polymers in very high yield while retaining high stereoregularity.
So far it has been known that some solid catalyst components used in polymerization of olefins contain magnesium, titanium, an electron donor compound and halogen as essential components. A large number of methods for olefin polymerization by polymerization or copolymerization of propylene, in the presence of a catalyst for olefin polymerization comprising the above solid catalyst components, an organoaluminum compound and organosilicon compound, have been proposed. For example, Japanese Unexamined Patent Publication No. (herein after referred to as JP-A) 57-63310/1982 and JP-A 57-63311/1982 disclose a method for polymerization of olefins of 3 carbon atoms or more, in which a combined catalyst comprising solid catalyst components containing a magnesium compound, titanium compound and an electron donor such as diester compound, e.g., phthalic acid ester, and an organoaluminum compound and an organosilicon compound having a Sixe2x80x94Oxe2x80x94C linkage is used.
JP-A 1-6006/1989 discloses solid catalyst components for olefin polymerization, which contain a dialkoxymagnesium, titanium tetrachloride, and dibutyl phthalate, wherein propylene is somewhat effectively polymerized in the presence of the solid catalyst components to give a stereoregular polymer in high yield. In this situation, the polymers produced with the above catalysts have been utilized in various ways as molding products such as cars and household electric appliances as well as containers and films. In producing these products, polymer powder is melted and molded in anyone of various forming machines. Particularly, in producing large-sized molding products by means of injection molding, high fluidity (melt flow rate) of melted polymers is sometimes required, and many researches have been continued accordingly in order to enhance the melt flow rate of polymers.
The melt flow rate greatly depends on the molecular weight of polymers. In the polymer trade, it is general to add hydrogen as a molecular weight regulator for the polymer produced in polymerization of olefins. When low molecular weight polymers are produced, i.e., in order to produce polymers of high melt flow rate, a large quantity of hydrogen is usually added, though there is a limitation in a pressure reactor in terms of safety as well as in an adaptable amount of hydrogen. In order to add a much more amount of hydrogen, the partial pressure of monomer to be polymerized has to be decreased, but decrease of the partial pressure is accompanied by decrease of productivity. Additionally, use of a large amount of hydrogen may bring about a problem of cost. It has been desired, accordingly, that a catalyst capable of producing polymers of high melt flow rate with a lesser amount of hydrogen could be developed. In other words, a catalyst which has a high activity to hydrogen or high responsiveness to hydrogen and which gives a highly stereoregular polymer in high yield is expected to be developed. In the above-mentioned prior art, however, it is not sufficient to solve such a problem.
That is, the purpose of the present invention is to solve such a problem remaining in the prior art and to provide a solid catalyst component and catalyst for polymerization of olefins, which can afford olefin polymers in very high yield, in particular, which can afford propylene polymers in very high yield while retaining high stereoregularity, and which have a high responsiveness to hydrogen.
The present inventors worked assiduously to solve the problems remaining in the above-mentioned prior art and found that a solid catalyst component comprising a magnesium compound, titanium tetrachloride, and a particular phthalic acid diester or a derivative thereof exhibit very high activity in polymerization of olefins, particularly in polymerization of propylene to give propylene polymers in high yield with retaining a high stereoregularity, and moreover the components have high competence to hydrogen. Thus, the invention was completed.
That is, the solid catalyst component (hereinafter sometimes referred to as xe2x80x9ccomponent (A)xe2x80x9d) for polymerization of olefins to attain the above-mentioned purpose according to the present invention are characterized in that they comprise (a) a magnesium compound, (b) titanium tetrachloride, and (c) a phthalic acid diester or a derivative thereof of the following general formula (1): 
(wherein R1 is an alkyl group of 1 to 8 carbon atoms or halogen atom; R2 and R3 are the same or different, representing an alkyl group of 1 to 12 carbon atoms; the number n of the substituent R1 is 0, 1 or 2, and when n is 2, R1 may be the same or different; provided that when n is 0, R2 and R3 each is an alkyl group of 4 to 8 carbon atoms having a tertiary carbon atom).
Moreover, the catalysts for polymerization of olefins in the present invention comprise:
(A) the above-mentioned solid catalyst components for polymerization of olefins;
(B) an organoaluminum compound of the following general formula (2):
R4pAlQ3xe2x88x92pxe2x80x83xe2x80x83(2)
(wherein R4 is an alkyl group of 1 to 4 carbon atoms; Q is hydrogen atom or halogen atom; and p is an integer of 0 less than pxe2x89xa63); and
(C) an organosilicon compound of the following general formula (3):
R5qSi(OR6)4xe2x88x92qxe2x80x83xe2x80x83(3)
(wherein R5 is the same or different, representing an alkyl group of 1 to 12 carbon atoms, a cycloalkyl group, a phenyl group, a vinyl group, an allyl group, or an aralkyl group; R6 is the same or different, representing an alkyl group of 1 to 4 carbon atoms, a cycloalkyl group, a phenyl group, a vinyl group, an allyl group, or an aralkyl group; q is an integer of 0xe2x89xa6qxe2x89xa63).